Electron gun



394& I P. A. SNELL 2,467,506

ELECTRON GUN Filed Aug. 4, 1944 FIGJ W a INVENTOR PHILIP ASNELL Patented Apr. 19, 1949 ELECTRON GUN Philip A. Snell, Fort Wayne, Incl., assignor, by mesne assignments, to Farnsworth Research Corporation, a corporaton of Indiana Application August 4, 1944, Serial No. 54.8,053

2 Claims.

This invention relates enerally to electron gun structures for cathode ray-tubes and is particularly directed to supportin structure for electrodes in electron-gun structures.

Heretofore, in the prior art, the various electrodes of an electron gun are supported by numerous rods, spacers and clamps. This structure is difiicult to manufacture. Under normal operating conditions, the supports are subjected to extreme variations of temperature and, therefore, to bending and warping, with the result that the combined expansion of all the supports causes distortion and misalignment of the electrodes. Also, in prior art devices means are frequently provided to rigidly support only one end of the gun element, whereby it is unbalanced and unduly affected by normal vibration. Vibration of the electrodes during the operation of the tube may cause spurious signals or image distortions which are plainly visible.

In other conventional gun structures, the multiple electrodes of the gun are supported at the mid-point of an intermediate eiectrode. In this type of structure, upon heating of the tube, the independent expansion and warping of the electrodes is not compensated with the result that the alignment of each electrode may be changed to adversely affect the operation of the tube.

It is an object of this invention to provide an improved electron-gun structure wherein the electrodes of the gun are rigidly supported and wherein the supports are so constructed that heat expansion has substantially no effect on the alignment of the electrodes.

Whereas in the prior art each electrode of an electron gun usually is individually supported from the tube envelope, there is provided, in accordance with this invention, individual supports secured to and exten-:ling between acljacent electrodes so that the entire structure is a unit. This structure prevents variation of temperature from causing misalignment of the electrodes. The unit is supported within the tube envelope at one end thereof by a set of supports extending into the re-entrant portion of the envelope. Another set of supports is arranged at the other end of the unit in tangential relation thereto, each. support extending into engagernent with the envelope. The characteristics of this structure are such that vibratory motion of the tube cannot affect the relative position of the unit within the tube.

For a better understanding of the invention, together with other andfurther objects thereof, reference is made to the following description, taken in connection with the accompanying draw ing, and its scope will be pointed out in the appended claims.

In the accompanying drawing:

Fig. 1 is an elevational view of a cathode-ray tube with parts broken away to show an electron gun mounted within the envelope.

Fig. 2 is an enlarged sectional view taken on lines 2--2 on Fig. 1,

Fig. 3 is a sectional view taken on line 3--3 on Fig. 2.

Fig. 4 is a sectional View taken on lines 4-4 on Fig. 2.

Referring to the drawings, there is shown a cathode-ray tube l having an envelope 2. Arranged in the envelope is an electron gun 3 for generating and directing an electron beam towards a fiuorescent screen 4.

The electron-gun assembly comprises an electron-emitting cathode 5, a control electrode 6 and first and second accelerating anodes 'I and 8. For avoiding unnecessary complication, the external conductors for the various electrodes have been omitted. Near the ends of the first anode 1, there is secured thereto, by spot welding or other suitable means, a plurality of supporting rods such as 9 and IE.

At the forward end of the grid 6, there is secured thereon supporting rods ll which are arranged in alignment with ends of the rods 9 of the anode 1. Extending rearwardly from the anode 8 are suppo rting rods l5. Rods 9 and ll are insulated from one another and also connected by glass beads !6. Rods !4 and !5 are similarly insulated and connected by glass beads Il. It is to be observed that the anode 'l is rigidly supported at its ends by the grid and the second anode 8 and also insulated therefrom. This arrangement prevents any relative lateral movement of the electrodes, and during heating of the tube the direction of expansion is in one direction. Since the expansion of the electrodes is in one direction, their spatial relationship is unchanged whereby there cannot be any distortion of the electron beam.

Extending rearwardly from the cathode 5 are supporting rods !8. Projecting from the rearward end of the grid 6 are supporting rods l9. At the ends of rods |8 and l9 there are fused thereon glass beads Zi for rigidly supporting and insulating the cathode within the grid. It is to be observed that the cathode is illustrated as an integral part of the gun structure and is supported thereby. This arrangement permits accurate alignment of the cathode with respect to the grid prior to the installation of the gun structure within the tube. Since the signal is directly ap- 3 plied to the cathode and the grid, it is therefore necessary to have said electrodes accurately aligned.

In my invention it is also to be noted that the cathode during the heating of the tube is arranged 'io-r movement in one direction as are the other cooperating electrodes, whereby the spatial relationship of the whole gun structure is unchanged and no distortion of the electron beam is caused.

Extending rearwardly ;from and Secured to the grid 6 are gun-supporting rods 22, the rearward ends of which are anchored in the re-entrant portion of the envelope for supporting one end of the gun assembly.

connected tangentially to the forward end of the anode 8 are another group of gun-supporting rods 23, the outer ends of which are provided with fused glass beads 24. The glass lbeads 24 are also fused to the inner Wall of the envelope for rigidly supporting the forward end of the gun structure. This rigid Construction prevents the gun assembly from vibrating and causing distortion of the beam.

In assembling the structure described hereinbefore, the grid 6, anodes 'I and 8 and the cathode 5 are secured to one another prior to installation of the gun within the tube envelope. Therefore, it is possible to align the elect'odes in a jig or other suitable means and attach them to one another whereby to attain extremely accurate alignment. Thereafter, the electron gun as a whole may be inserted within the tube envelope and secured the-reto 'by the rods 22 and 23. In

view of the fact that the electrodes are rigdly Secured to one another, any expansion thereof can only result in an overall increase in length of the whole electron gun. There is substantially no change in spatial relationshi-p between individual electrodes. Any overall increase in length of the gun does not change its position relative to the tube envelope by reason of the tangential connection of rods 23 to anode 8. Thus, in accordance with this invention there is provided an electron gun for generating an electron beam which is substantially free from distortion such as may be expected to result from mechan-ical 'shocks or from relative displacement of the gun elements.

While there has been described what is at present consi-dered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appendedclaims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A cathode-ray tube having an envelope containing an electron gun comprising a plurality of electrodes and rigid supporting means connected between adjacent ends of said electrodes, and rigid supporting means connected between each end of said electron gun and said envelope and comprising members connected substantially tangentially with respect to one end oi said gun and said envelope for rigtidly supporting said electron gun within the envelope.

2. A cathode-ray tube having an envelope containing a unitary electron gun assembly comprising a plurality of electrodes, rigid supporting means connected between adjacent ends of said electrodes, and rigid supporting means connected from two of said electrodes to said envelope and comprising members connected substantially tangentially with respect to one 'end of said gun and said envelope for rigidly supporting the electron gun assembly within the tube.

PHILIP A. SNELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 22,378 Bowie Sept. 21, 1943 1,973,606 Bullimore et al. sept. 11, 1934 2,088,493 Sutherlin et al July 27, 1937 2,139,678 Glass Dec. 13, 1938 2,378,569 Messner June 19, 1945 FOREIGN PATENTS Number Country Date 507340 Great Britain Nov. 10, 1938 

